zacm

1 hour ago, MarkAR said:

Amp glow is pretty much the norm for CMOS I believe. Calibration frames will deal with it.

Cheers, Mark!

11 minutes ago, david_taurus83 said:

As already mentioned, thats normal. Dark frame subtraction will remove the same glow from your light frames. I used to take 15 minute Ha frames and never had an issue removing amp glow with matching darks.

Thanks, David, appreciate you taking the time to post.

19 minutes ago, vlaiv said:

This is rather normal and should not worry you. In fact, level of dark current is really low and corresponding dark noise is comparable to read noise in magnitude in exposures up to 5 or so minutes.

Most important thing - it calibrates out nicely when calibrating properly.

Here is stack of 16 dark subs from my ASI1600mm (version 2 not pro) at gain 139 / offset 64 / 240s scaled down and stretched to show amp glow:

I have no issues with amp glow in my images after calibration.

Thank you so much Vlaiv, I really appreciate the reassurance. 

5 minutes ago, fwm891 said:

Don't know the camera but you may be getting problems with the cooling if you've covered it completely. I have a 294MC Pro and I did exactly that to get dark, darks but the camera virtually over heated very quickly and poiwer usage was at 100% which is too high. Try and keep to circa 75% or less. I found that just putting the cap on and covering the cap with foil was all that was needed. That way the ventilation grills are open and the camera can disipate the heat from the cooling.

Thanks Francis. The only good news was that every frame was perfectly uniform despite my experimentation and the results were exactly as shown above. Initially I just had the scope on the kitchen table with the cap on and the lights off and the result was exactly the same so definitely not an overheating issue, but I note your point about not doing anything that will prevent the camera from breathing.

Posted this on CloudyNights this morning, but I dont seem to have a lot of luck on that forum which is a shame as everyone seems really helpful on there..

My ZWO power supply showed up yesterday so I was able to start building a dark library for my new ASI1600GT while I wait for my filters to arrive.

My excitement soon turned to disappointment when I applied a screen transfer stretch in Pixsinsight to the first 360 second dark frame which revealed an almost vignette style amp glow.

Initially I thought it was light leakage so tried various things to completely rule that out. The last was to remove the camera from the scope, screw the cap on, place the camera nose down in wooden box, close the lid and drape the box with blackout material in a completely dark room - same result.

Is this really as good as it gets? My budget Canon EOS 2000D cost £290 and had no amp glow. $1700 later and I am swimming in it. Am sure it can all be calibrated out, but kinda gutted to have spent that sort of money to get this sort of result.

I emailed the photo below to ZWO who replied this morning to say this is normal and gave a link to a help article about calibrating out amp glow which I had already read.

Just looking for some reassurance really as it doesn't feel that normal having just spent $1700 on my dream astro camera....

Exposure time: 360 seconds
Gain: Unitary (139)
Offset 50
USB Limit 40 (I also tried 90 but it was the same).
Temperature -15c

Tried USB2 and USB3